1. Field of the Invention
The present invention relates generally to methods for depositing materials upon a semiconductor substrate, and more particularly to a two step deposition process wherein the first step includes a collimated relatively low temperature sputtering process and the second step utilizes a standard high temperature sputtering process.
2. Brief Description of the Prior Art
A standard process step in the manufacturing of integrated circuits involves the deposition of a metallic layer upon the surface of a wafer. Typically, the wafer surface has been previously etched in a plurality of locations, whereby the surface contains holes and grooves and is therefore not planar. It is the goal of the deposition step to uniformly and completely fill the holes and grooves and to achieve a generally planar outer surface after deposition has occurred. However, it is difficult to completely fill the holes and grooves, such that no voids exist. As is well known, the existence of voids can result in poor performance and defective devices. In an attempt to solve this problem, the prior art utilizes a deposition substrate temperature of approximately the melting point of the deposition material (approximately 450 degrees C. for aluminum) such that the deposited layer will tend to flow and completely fill the holes and grooves. The success of this process relies to a great extent upon the achievement of a uniform temperature throughout the substrate, such that the deposition and flow of the deposited material is substantially uniform and controlled. However, achieving a uniform temperature throughout the substrate requires rigorous temperature controls and can be difficult and time consuming.